Manufacture of crotonic acid



was

2,945,058 Patented July 12, 1960 ice such a rate that the composition of the gas circulating within the system will be approximately 8 percent oxygen.

However, a range of 1-25 percent is satisfactory for operation. r z 945 05s The temperatures within the autoclave may range from 15 to 25 C. and the proportion of solvent to crotonalde- MANUFACTURE OF CROTONIC ACID 5 hyde may be from 20-60 percent solvent to 40-80 percent crotonaldehyde. Other solvents other than heptane which fi g gfgfg i p g ig i ig ggk ggfg ggf gaggf may be used include such inert solvents as hexane, isoester, NY" a corporation of New Jersey 7 propyl acetate, toluene, ethyl acetate, acetoneand acetic 7 acid and the like. The particular inert solvent is not criti- NO Dlawing- Filed p 1957! 633,213 10 cal, but we prefer nonpolar solvents such as hydrocar- 'bons. 7 Claims 260-439) The following data illustrates our reaction compared with that shown in the prior art.

Run A as follows was made with crotonaldehyde which This invention concerns the manufacture o firOt c had been dried by distillation and dissolved in benzene add y the Oxidation of crotonaldehyde With molecular to form a percent solution, after which air was passed oxygen. through the solution for 14 hours in order to obtain It is known to manufacture organic acids from aldecrotonic acid. As can be seen from the ,table, the yield hydes by the oxidation of the aldehydes to the acids. was 64 percent. Run B followed also the general meth- Crotonaldehyde has been used as a starting materialfor 20 ed as in run A but used a much higher ratio of crotonsuch an oxidation in order to obtain crotonic acid. In aldhyde to solvent, and the solvent used was heptane this process diluents such as hydrocarbons, esters, ketones inst d of benzene, However, instead of impro in the and organic acids have been used in the presence of a yield as would be expected, the yield was only 38 percatalyst such as a cobalt, manganese and copper acetate cent. at to C. as stated in US. Patent 2,413,235 with 25 Run C was run according to our process using wet yields reported at 7-0 percent. crotonaldehyde dissolved in heptane.

Ratio of Lbs. Acetic Lbs.- Percent C. Timein Crotonal- Acid per lb. Residue Percent Run H Oin Temp. Hours dehyde to Crotonic per 1b. of Yield Feed Solvent Acid Crotonic Acid A o. 5 so 14 0. 3 0. 2 0. 0a 64 B 0. 5 so 14 3. 0 0. 55 o. 71 as o 12.0 20 s 3.0 0.1 0.05 92 US. Patent 2,487,188 claims a process in which As illustrated above, it is clear that our process gives crotonic acid is obtained by oxidizing crotonaldehyde in much higher yields with less formation of by-product the presence of manganese acetate and potassium. peracetic acid and residue than the prior art methods using manganate in acetic acid at 5 to 10 C. with oxygen with y srotonaldebyde and a Catalyst t lo s yields reported at 78 percent. U.S. Patent 2,577,829 amples are intended to illustrate our invention but not to claims aliquid phase oxidation process in ligroin using imit'it in any way. i a catalyst of tertiary butyl peroxide with yieldsreported Example 1 at 62 to 72 percent. 1 Three volumes of crotonaldehyde containing 88 per- HOWBVBI', due oxidation to undesirable y-p cent crotonaldehyde and 12 percent water, containing 520 bets, b01111 10W-b0i1i11g and high-boiling, maximum Y grams of crotonaldehyde were dissolved in 140 grams of according to the Prior all have been reported at 80 P hexane and oxidized in a glass oxidation tower equipped cent. a with a circulation arm for 8 hours with air at 18 C. Catalysts have normally been employed in the ai After 8 hours the conversion to crotonic acid was 23 peroxidation of low-molecular weight aldehydes to cat-. t, Th idati product w s then charged to a fllyle the smooth decomposition of P Y compounds crotonaldehyde azeotrope recovery column at reduced and to prevent building up a dangerou ly high c n npressure with sufficient water to obtain approximately a nation of peroxy compounds. However, withour process 50 percent crotonic acid mixture in the stripped base. We have Obtained high Yields other than o e reported Crotonic acid must be kept below 130 C. to prevent in the prior art and we have also reduced the f-ormapolymerization. Therefore, with the addition of suificient tion of undesirable by-products to 0.540 percent. water this recovery step of crotonaldehyde and solvent can One object of our invention is to provide a process be performed at atmospheric pressure. for the molecular oxygen oxidation of crotonaldehyde The stripped base was then cooled to 05 C. where to crotonic acid in high yields of from 85-96 percent. white crystals of crotonic acid were obtained, melting Another object is to provide a process for manufacturpoint 70-72 C., which represented approximately 80 ing crotonic acid which is 'efiicent and economical to oppercent of the crotonic acid. The filtrate was then exerate. tracted with an equal volume of a isopropyl acetate which In the practice of our invention, wet crotonaldehyde is a suitable polar solvent. The extract was then distilled which contains about 13 percent water is dissolved in for recovery of isopropyl acetate and crotonic acid. The a solvent such as heptane in a ratio of about one-quarter recovered isopropyl acetate contained the low-boiling bysolvent to three-quarters crotonaldehyde. The mixture products and the residue contained the high-boiling byis fed into an autoclave in which an oxygen-containing products, gas is fed at a temperature of about 20 C. and at pres- It is understood, of course, that this process could be sures of 50400 Pounds gauge- Air can be used as h run continuously by recycling recovered crotonaldehyde, Oxygen-containing g and is Preferably introduced t and isopropyl acetate.- The low-boiling by-p'roducts which are mainly acetic acid can be removed by distillation.

Example 2 The same ratio and weights of crotonaldehyde to hexane was used as in Example 1 but the oxidation was car- 15 ried outat 35 C. for 8 hours. Conversion and yield obtained was 34.4 percent and 82.5 percent respectively while conversion to acetic acid was 10.4 percent and to residue 2.2 percent. This run indicated the increase in by-products when oxidized at a higher temperature. 20

Example 3 I A series of four runs was made using a 3/1 ratio of a 88 percent crotonaldehyde-water azeotrope to heptane V (boiling point 95-100 C.) at 20 C. for 8 hours. The 25 runs were distilled by reduced pressure distillation at 100 mm. of mercury, and the recovered crotonaldehyde and heptane recycled three times. The crotonic acid produced was distilled at a pressure of 50 mm. of mercury. An 87.2 percent yield was obtained with a 3.4 percent 30 conversion to acetic acid and 6 percent conversion to residue.

The following table illustrates the results obtained using our process showing use of variations in the conditions within the range given above and also showing the use 5 of various solvents.

We claim:

1. A process for the production of crotonic acid comprising the oxidation of crotonaldehyde in the absence of an added catalyst by incorporating a mixture of crotonaldehyde and water which contains 5-15 water in an inert solvent selected from the class consisting of hexane, heptane and toluene so that 20-60% of the resulting liquid by weight is the inert solvent, and contacting with an oxygen containing gas having 1-25% molecular oxygen at a temperature of 15-25 C.

2. A process for the manufacture of crotonic acid in the absence of an added catalyst comprising continuously feeding a mixture of crotonaldehyde containing 5-15 water and 20-60% based on the resulting mixture of an inert solvent selected from the class consisting of hexane, heptane, and toluene into a reactor with an oxygen containing gas having 1-25% molecular oxygen under a pressure of 50-100 lbs. gauge in intimate contact with the oxygen containinggas at a temperature of 15-25 C. continuously withdrawing a proportion of the reaction mixture and recovering the crotonic acid therefrom.

3. A continuous process for the production of crotonic acid in the absence of an added catalyst comprising mixing crotonaldehyde containing 5-15 by weight water and heptane to form a mixture containing about 33% heptane and intimately contacting with an oxygen containing gas containing 8% molecular oxygen at a pressure of 50-100 lbs. gauge at a temperature of about 20 C.

4. A process for the production of erotonic acid comprising the oxidation of crotonaldehyde in the absence of an added catalyst by incorporating a mixture of crotonaldehyde and water which contains 5-15 water in hexane so that 20-60% of the resulting mixture by weight is hexane and intimately contacting with an oxygen con- Percent V V Percent v V Oxidation 7 Percent Converted Percent Solvent Solvent Time in Tempera- Yield of to Low Converted by Hours ture Crotonic Boilers to e Volume Acid (Acetic Residue Acid) Hexane 25 8 18 91. 5 3 0. 7 Do.-. 25 8 18 93. 5 3 0. 7 Do 25 8 18 88. 9 Do- 25 8 18 91. 3 0. 7 Do. 50 8 18 94. 0 3 0. 7 Do- 50 8 18 95. 0 0. 4 Do- 10 8 18 84. 5 2. 5 0. 8 Do. 20 8 18 84. 9 3. O 0. 9 D0... 33 8 18 v 91. 2 3.0 0. 9

Toluene- 8 18 96. 5 2. 8 0. 6 None.-. 0 8 18 64.0 2. 3 0. 5

Acetic Acrd 25 8 18 85. 8 1 1 .Isopropyl Acetat 25 8 18 91. 3 3. 7 0.3

Ethyl Acetate 25 8 18 88. 0 2. 6 0. 5

Heptane 25 8 2O 87. 2 3. 4 6, 0

Hexane 25 8 82. 5 10. 4 2. 2 D0 25 15 20 82. 7 3. 4 0,6

ever, this phase of the process is not critical and may be carried out in various ways. Our process may be carried on either batchwise or continuously; the solvent-croton- "aldehyde mixture is continuously fed to a tower, reactor or" autoclave where it is contacted intimately with an oxygen-containing gas. The gas which is removed from the oxidizer is passed through a condenser Where the material such as crotonaldehyde and crotonic acid are removed and the oxygen-containing gas recycled back to the oxidizer after being'enriched with additional oxygencOntaining gas. 1

taining gas having 1-25% molecular oxygen at a temperature of 15-25 C.

5. A process for the production of crotonic acid comprising the oxidation of crotonaldehyde in the absence of an added catalyst by incorporating a mixture of crotonaldehyde andwater which contains 5-15% water in heptane so that 20-60% of the resulting mixture by weight is heptane and intimately contacting with an oxygen con taining gas having 1-25% molecular oxygen at a temperature of l5-25 C.

6. A process for the production of crotonic acid comprising the oxidation of crotonaldehyde in the absence of an added catalyst by incorporating a mixture of crotonaldehyde and water which contains 5-15 water in toluene so that 20-60% of the resulting mixture by weight is toluene and contacting with an oxygen containing gas having 1-25% molecular oxygen at a temperature of 15-25 C.

7. A process for the production of crotonic acid comprising the oxidation of crotonaldehyde in the absence of an added catalyst by incorporating a mixture of crotonaldehyde and water which contains 5-15 water in an inert solvent selected from the class consisting of hexane, heptane and toluene so that 20-50% of the resulting mixture by weight is the inert solvent and containing an References Cited in the file of this patent UNITED STATES PATENTS Staudinger et a1. June 5, 1945 Kennedy Dec. 24, 1946 

1. A PROCESS FOR THE PRODUCTION OF CROTONIC ACID COMPRISING THE OXIDATION OF CROTONALDEHYDE IN THE ABSENCE OF AN ADDED CATALYST BY INCORPORATING A MIXTURE OF CROTONALDEHYDE AND WATER WHICH CONTAINS 5-15% WATER IN AN INERT SOLVENT SELECTED FROM THE CLASS CONSISTING OF HEXANE, HEPTANE AND TOLUENE SO THAT 20-60% OF THE RESULTING LIQUID BY WEIGHT IS THE INERT SOLVENT, AND CONTACTING WITH AN OXYGEN CONTAINING GAS HAVING 1-25% MOLECULAR OXYGEN AT A TEMPERATURE OF 15-25*C. 